The present invention relates generally to improvements in seat belt buckles, and more particularly to seat belt buckles which are suitable for use in motor vehicles.
A seat belt buckle provides a readily releasable mechanism for securing the ends of a seat belt and/or shoulder belt in a predetermined position to restrain an occupant of a vehicle during a collision.
One form of seat belt buckle in use particularly in Europe has a side operated push button rather than a top push button and employs a lock pin or latch bar which is positioned to block release of a latching pawl from locking engagement with a tongue plate until the push button is operated. Usually, the lock pin or bar is mounted to slide in slots in the frame and is shifted by movement of the push button from a blocking position over the latch pawl to a release position in which the latch pawl is free to pivot from latching engagement with the tongue plate. In such buckles, the push button is typically biased toward an outer position and is pushed inward to open the latch mechanism.
One example of a seat belt buckle is given in U.S. Pat. No. 4,562,625 issued Jan. 7, 1986 to Gerald A. Doty and William E. Hunter, of which the present invention is an improvement. One major feature of U.S. Pat. No. 4,562,625 is the single tension spring which is employed to perform various needed functions, such as biasing a latching member in both open and closed positions, as well as biasing a push button to its normal, outward extending position. While the seat belt buckle described therein has been very successful, certain refinements could lead to even greater cost savings, especially since seat belts of this kind are produced in large numbers for use as original equipment on automobiles. Even relatively minor savings in the cost of each unit, can make a substantial difference in the commercial success of the seat belt design.
Attention is directed herein to desired improvements which are principally concerned with the so-called actuating system which interconnects the single spring mentioned above, with a first member for ejecting a tongue plate from the seat belt latch, and a second member for locking a tongue-engaging latch. The actuation system includes a pair of rigid links which are fastened to the ends of a first cylindrical pin which locks the tongue-engaging latch. The links are also fastened to the ends of another cylindrical pin which ejects the tongue plate from the buckle.
The bottom portions of the rigid links and the ends of the cylindrical pin which ejects the tongue plate ride along slots formed in the latch frame. It is particularly desirable if any frictional forces generated between these members and the slotted latch frame could be reduced or eliminated.
Improved control over movement of the tongue plate ejecting pin, would be welcomed as an improvement in fail-safe operation of the seat belt buckle.
The actuation system of U.S. Pat. No. 4,562,625 further includes a wire-formed retainer having arms which extend outside the frame, between the frame and a plastic cover, for attachment to the rigid links. The retainer arms move back and forth, as they follow the links during operation of the seat belt buckle, in a relatively narrow gap formed between the frame and cover. If the retainer could be entirely contained within the frame, then the risk of jamming the retainer between the frame and cover would be reduced, particularly when a 40G load is applied to the side of the buckle as is done in some tests for automotive companies and/or governmental agencies. Additionally, this allows the frame to be made wider and more massive so that it may withstand heavier loads without increasing the width of the cover.
Further improvements could also be made if the wire-formed retainer could be replaced with a more rigid structure, to prevent warping during assembly or operation of the seat belt. A rigid structure would also offer improved pivotal support for the links, as opposed to L-shaped bends formed in the ends of the retainer member.
Any separate preassembly steps that can be eliminated can lead to considerable cost savings. In particular, it would be advantageous if construction of the link assembly could be simplified, or even formed of a single molded part.